Machine tool coordinate system is the basic coordinate system used to determine the workpiece coordinate system. It is an inherent coordinate system on the machine tool and has a fixed coordinate origin.
If the servo motor adopts incremental encoder, it needs to return to zero every time the machine tool is turned on to find the zero point of the machine tool coordinate system.
However, the servo motor with absolute encoder does not need to return to zero every time the machine tool is turned on, and it has zero memory function after power off.
Question 2: What is the difference between the machine tool coordinate system and the workpiece coordinate system? Lathe is divided into tool setting and tool setting, but the principle of tool setting is the same. Assume that there is no tool aligner.
The lathe itself has a mechanical origin, so you usually try to cut the tool. For example, after cutting the outside diameter of the lathe, you should exit in the Z direction, measure the outside diameter of the lathe, then find the number of the tool you are using in the G diagram, move the cursor to X, and enter X ... You will know the tip position of this tool position according to the measuring machine tool, and the inside diameter is the same, so the Z direction is simple. Just touch each tool in the z direction and measure Z0.
In this way, all the knives are recorded, and the machining zero point is determined to be offset, so any knife can determine the origin of the workpiece.
Remember to look at the knife before aiming.
A more convenient method is to align the tool with the chuck. We know the outside diameter of the chuck, and the tool can touch the input outside diameter. When finding the right inner diameter, you can press a measuring block on the chuck by hand and input the outer diameter of the chuck.
It would be much more convenient if there is a tool setting instrument, which is equivalent to a fixed tool setting instrument to try to cut the workpiece. When the tool touches it, the position is recorded.
Therefore, if it is a variety of small batch processing, it is best to buy a suitable tool. It saves time.
On the MAZAK lathe I used before, I changed a new workpiece and started to process new workpieces in batches (including the soft claw trial cutting of tool changing), which generally takes only 10 to 15 minutes.
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Basic coordinate relationship of CNC lathe and comparison of several tool alignment methods
In the process of NC lathe operation and programming, it is very important to understand the basic coordinate relationship and the principle of tool alignment. This is very helpful for us to better understand the machining principle of machine tools and correct the dimensional deviation in machining.
First, the basic coordinate relationship
Generally speaking, there are two commonly used coordinate systems: one is mechanical coordinate system; The other is workpiece coordinate system, also called program coordinate system.
There is a fixed reference point (assuming (x, z)) in the mechanical coordinate system of the machine tool. The function of this reference point is mainly used to locate the machine itself. Because the system sets the current position to (0,0) no matter where the tool rest stays after each boot, which will inevitably lead to inconsistent benchmarks, the first step of each boot is to return to the reference point (some are called zero return), that is, to determine the origin (0,0) by determining (x, z).
For the convenience of calculation and programming, we usually set the origin of the program at the rotation center of the right end face of the workpiece, so as to make the programming datum coincide with the design and assembly datum as much as possible. The mechanical coordinate system is the only benchmark of the machine tool, so it is necessary to find out the position of the program origin in the mechanical coordinate system. This is usually done in the next tool setting process.
Second, the knife method
1. Try to cut the knife.
Trial cutting method is the most widely used tool setting method in practice. Taking Mitsubishi 50L CNC system RFCZ 12 lathe as an example, the specific operation method is introduced.
After the workpiece and the cutter are clamped, the spindle is driven to rotate and the tool rest is moved until the workpiece tries to cut a section of excircle. Then keep the X coordinate unchanged, move the Z-axis tool away from the workpiece and measure the diameter of the excircle. Input the corresponding tool parameters into the tool length, and the system will automatically subtract the excircle diameter from the current X coordinate of the tool to get the X origin position of the workpiece coordinate system. Then move the tool to try to cut the end face of one end of the workpiece, and enter Z0 in the corresponding tool parameter width. The system will automatically subtract the value just entered from the Z coordinate of the tool at this time to get the position of the Z origin of the workpiece coordinate system.
For example, when x is 150.0 and the diameter of the excircle turned by the handle of No.2 tool is 25.0, the value of the program origin when cutting with this tool is150.0-25.0 =125.0; When z is 180.0, the end face of the tool rest is 0, so the z value of the program origin when cutting with this tool is 180.0-0= 180.0. (125.0, 180.0) are stored in x and z in the parameter length of 2# tool respectively, and the workpiece coordinate system is successfully established by using T0202 in the program.
In fact, to find the position of the origin of the workpiece in the mechanical coordinate system is not to find the actual position of the point, but to find the position of the tool rest when the tool tip reaches (0,0). This method generally does not use standard knives, and all the knives to be used need to be aligned before processing.
2. Tool setting instrument automatic setting tool
Nowadays, many lathes are equipped with ...
Question 3: What is the coordinate system of CNC machine tools? Numerical control machine tool (global machinery) adopts spatial rectangular coordinate system X axis Y axis Z axis.
Question 4: What is the relationship between the machine tool coordinate system and the workpiece coordinate system? The coordinate system of NC machining machine tool is mainly divided into machine tool coordinate system and workpiece coordinate system. The coordinate system of machine tool is a coordinate system established by the hardware system of machine tool, which is established by the zero point of grating or encoder fixed on the machine tool itself. In CNC machine tools, G53 is generally used as the machine coordinate system. The workpiece coordinate system is artificially set on the basis of the machine tool coordinate system, that is, a new coordinate system is established in the machine tool coordinate system, such as G54-G59, G54. 1, G54.2, etc. Workpiece coordinate system is a temporary coordinate system set for the convenience of workpiece processing, which can be changed at any time through the coordinate system setting interface. Which coordinate system is adopted by CNC machine tools depends on which coordinate system is selected in the machining program.
Question 5: What do machine tool coordinates, mechanical coordinates, relative coordinates and absolute coordinates mean? Mechanical coordinates and machine tool coordinates are the same concept.
This is the fixed point set by the machine tool manufacturer according to the needs.
Its value is set by the manufacturer.
When our machine tool returns to the reference point, its value is X0. Y0.Z0 (I take the machining center as an example).
Then the value of the tool we refer to is related to the machine tool coordinates.
"In other words, our tool alignment is based on the value of machine tool coordinates."
When machining a workpiece, we must establish the workpiece coordinate system G54.
So this point is the coordinate point we programmed,
We will see a lot of data on the display interface of the operating machine tool.
A better machine tool displays four sets of data.
They are: machine tool coordinate values. Absolute coordinate values. Relative coordinate values. Coordinate values of the tolerance.
What do you mean?
Let's illustrate that the tool reaches a certain point.
Machine tool coordinates. Indicates the position of the tool in the machine tool.
Absolute coordinates. Indicates the position of the tool after programming to establish the workpiece coordinate system.
That is, the coordinate axis in our junior high school geometry is the same concept.
Its position has absolute value (1 quadrant, 2 quadrant. . . . )
Point G54 is the intersection of the X axis and the Y axis.
Relative coordinates. Indicates the position of the tool relative to G54.
It is a vector value, which is related to the direction. Generally speaking, we don't need to look at this set of data.
Tolerance coordinates. Indicates the number of tools that need to be finished in the machining process compared with the next process.
We usually associate the value of absolute coordinates with the origin of the program.
Question 6: What is the machine tool coordinate system? How to determine the coordinate axis of machine tool coordinate system 1 Machine Coordinate System
The machine tool coordinate system is the inherent coordinate system of the machine tool itself, which is generally set when the machine tool is used. The machine coordinate system is used to determine the position of the workpiece on the machine tool, the special position of the moving parts of the machine tool (such as tool changing point and reference point) and the range of motion (such as travel range and protected area).
The machine tool system adopts the standard Cartesian coordinate system and is established according to the following three principles:
(1) conforms to the right-handed rule.
As shown in Figure 7-2, the thumb points to the positive direction of the X axis, the index finger points to the positive direction of the Y axis, and the middle finger points to the Z direction; Or make a fist with your palm from the positive direction of X axis to the positive direction of Y axis and your thumb from the positive direction of Z axis.
Figure 7-2 Right-handed Rule
(2) The Z axis is in the same direction as the main axis.
The Z axis of most CNC machine tools is in the same direction as the spindle, but the positive direction of the Z axis should be determined according to two other principles. As shown in Figure 7-3 and Figure 7-4, the Z axis and its positive direction of a CNC lathe and a machining center are given.
(3) The direction of the tool away from the workpiece is the positive direction of the coordinate axis.
Different CNC machine tools have different forms of motion distribution. This principle emphasizes the relative motion direction between the tool and the workpiece. A more effective method is to take the origin of the machine coordinate system as a reference to determine whether the tool is far away from the workpiece.
It should be pointed out that when using these three principles to determine the machine tool coordinate system, these three principles must be considered at the same time, otherwise the correct machine tool coordinate system may not be obtained.
Question 7: What is the coordinate system of CNC machine tools? In CNC system, the movement of a specific point moving to a coordinate system can be described in absolute coordinate system or incremental (relative) coordinate system.
When compiling the machining program, according to the coordinate function of the numerical control system, the coordinate system is selected from the requirements of programming convenience (that is, dimensioning according to the part drawing) and machining accuracy.
Absolute coordinate system and incremental coordinate system can choose ISO standard and GB programming function instructions G90 and G9 1.
G90 indicates that the numerical value of the input size word is absolute value, G9 1 indicates that the numerical value of the input size word is incremental value, and the position values of the absolute value and the incremental value specify the target position corresponding to the coordinate system.
In the coordinate system, the distance or angle from the origin of the coordinate system to the position of the outline point of the part is called absolute size, and this coordinate system is called absolute coordinate system.
In the coordinate system, the position of the coordinate point is the coordinate increment value from the previous position, which is used to indicate the distance or angle, and the movement direction is specified by its symbol, which is called the increment value size. If it is a straight outline, it is equivalent to taking the starting point of the straight line (the end point of the previous process) as the coordinate origin, and the parallel lines parallel to the axis of the workpiece coordinate system establish a new coordinate system, which is called relative (incremental) coordinate system. If it is an arc outline, it is equivalent to establishing a relative coordinate system with the arc center as the coordinate origin.
Some numerical control systems do not need G9 1 instruction, but establish relative coordinate systems parallel to X, Y and Z at the starting point of motion. Its program is represented by G0 1 U_ V_ W_, which is equivalent to G9 1 X_ Y_ Z_.
In the part processing program, you can use the absolute value or incremental value, or the mixture of absolute value and incremental value, mainly to make the programmer can easily calculate the size of the program segment when programming.
Choosing absolute coordinate system or relative coordinate system for programming is related to the dimensioning method of part drawing.
Question 8: What are the machine tool coordinate system and the workpiece coordinate system? What are the main differences? Please answer simply! Thank you. The machine tool coordinate system is the machine tool's own coordinate system. It has been set at the factory and is fixed. It cannot be modified.
The workpiece coordinate system is set by the programming operator for the convenience of calculating the program coordinates, and can be modified.
Question 9: What determines the coordinate system of the machine tool? 1. Machine tool coordinate system.
The machine tool coordinate system is the inherent coordinate system of the machine tool itself, which is generally set when the machine tool is used. The machine coordinate system is used to determine the position of the workpiece on the machine tool, the special position of the moving parts of the machine tool (such as tool changing point and reference point) and the range of motion (such as travel range and protected area).
The machine tool system adopts the standard Cartesian coordinate system and is established according to the following three principles:
(1) conforms to the right-handed rule.
As shown in Figure 7-2, the thumb points to the positive direction of the X axis, the index finger points to the positive direction of the Y axis, and the middle finger points to the Z direction; Or make a fist with your palm from the positive direction of X axis to the positive direction of Y axis and your thumb from the positive direction of Z axis.
Figure 7-2 Right-handed Rule
(2) The Z axis is in the same direction as the main axis.
The Z axis of most CNC machine tools is in the same direction as the spindle, but the positive direction of the Z axis should be determined by considering the other two principles. As shown in Figure 7-3 and Figure 7-4, the Z axis and its positive direction of a CNC lathe and a machining center are given.
(3) The direction of the tool away from the workpiece is the positive direction of the coordinate axis.
Different CNC machine tools have different motion distribution forms, and this principle emphasizes the relative motion direction between the tool and the workpiece. A more effective method is to judge whether the tool is far away from the workpiece with the origin of the machine tool coordinate system as a reference.
It should be pointed out that when using these three principles to determine the machine tool coordinate system, these three principles must be considered at the same time, otherwise the correct machine tool coordinate system may not be obtained.
Question 10: What is the workpiece coordinate system and how to establish the lathe workpiece coordinate system? The machine coordinate system is a mechanical coordinate system. This coordinate system is fixed. Every time you start the machine, you actually let the guide rail touch the stop, and take this point as the zero point of the shaft. This is a process of establishment. The workpiece coordinate system is G54~~G59 coordinate system, which is set by the operator after the workpiece is ready. The set value is the position of the current point relative to the mechanical zero point, that is, the value in the current mechanical coordinate system. The local coordinate system seems to be used less. In FANUC system, it is G52 instruction (coordinate system offset). If G52 Xa Yb Zc is executed in G54 mode, the point (abc) of G54 coordinate system is the zero position of the new coordinate system. Without switching the coordinate system of the workpiece, all position instructions take this point as zero.